Method and apparatus for controlling anal incontinence

ABSTRACT

An electrostimulation probe comprising a suppository body formed with a rounded bulbous head, a reduced neck, and a broadened hilt, is inserted into the anus of a patient suffering from incontinence. The rounded bulbous tip and reduced neck facilitate anal insertion and subsequent retention. The rounded neck is clasped by the sphincter rectalis, and is provided with a pair of spaced electrical contacts which rest against the sphincter. The broadened hilt limits insertion of the suppository body, and has a substantially flat base so as to permit the patient to sit or lie down comfortably with the device inserted. A pair of electrical leads are connected respectively to the contacts, which are energized by a square wave signal having an average value of zero volts, a peak potential between 1 and 2 volts, and in the frequency range from about 18 to Hertz. 20 hertz. Such electrostimulation causes tonic and physiological contraction of the sphincter muscle, with significant results in the control of incontinence.

United States Patent Von Der Mozel 51 Mar. 21, 1972 [54] METHOD ANDAPPARATUS FOR CONTROLLING ANAL INCONTINENCE [21] Appl.No.: 752,352

FOREIGN PATENTS OR APPLICATIONS OTHER PUBLICATIONS Turner, Manual ofPractical Medical Electricity," 3rd Edition, 1902, p. 300 relied onPrimary Examiner-William E. Kamm Attorney-Hubbell, Cohen & Stiefel [57]ABSTRACT An electrostimulation probe comprising a suppository bodyformed with a rounded bulbous head, a reduced neck, and a broadenedhilt, is inserted into the anus of a patient suffering fromincontinence. The rounded bulbous tip and reduced neck facilitate analinsertion and subsequent retention. The rounded neck is clasped by thesphincter rectalis, and is provided with a pair of spaced electricalcontacts which rest against the sphincter. The broadened hilt limitsinsertion of the suppository body, and has a substantially flat base soas to permit the patient to sit or lie down comfortably with the deviceinserted. A pair of electrical leads are connected respectively to thecontacts, which are energized by a square wave signal having an averagevalue of zero volts, a peak potential between 1 and 2 volts, and in thefrequency range from about 18 to Hertz. 20 hertz. Suchelectrostimulation causes tonic and physiological contraction of thesphincter muscle, with significant results in the control ofincontinence.

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HANS A. VON DER MOSEL AT TOR NEYS PATENTED MR 21 W2 PATENTEDHARZI m2SHEET 3 BF 3 jil/y NORMflL RESPONSE PEHK vaL 7/765 (20//z) PHRHPL EG/CHES I a/V55 m r 6 d M V n 5 H 2 z 4 5 6 7 s 9 10 PEHA v04 mes (20 Hz)METHOD AND APPARATUS FOR CONTROLLING ANAL INCONTINENCE FIELD OF THEINVENTION This invention relates generally to the area of prostheticassistance, and particularly concerns the control of anal incontinenceby electrical stimulation of the sphincter rectalis.

THE PRIOR ART The general idea of electrical stimulation of muscletissue has a long history, and recently has culminated in the impressivesuccesses now achieved in the area of cardiac pacemaking. In otherrespects, however, electrical muscle stimulation is still largelyexperimental, and has not become an established therapeutic procedure.

Anal incontinence is a condition of considerable physical inconvenienceand psychological embarrassment which afflicts some patients, generallyas a result of neurogenic failure, or in some cases senile atrophy ofthe sphincter muscle. It is highly desirable that some way be found forcontrolling this condition.

In experiments with electrical stimulation of the sphincter rectalis tocontrol this condition, it was discovered that the techniques employedin the area of cardiac pacemaking and other electrical musclestimulation procedures are not applicable. Anal incontinence presents adistinct problem calling for a different kind of electrical musclestimulation, if anal incontinence is to be controlled effectively bythis means.

In cardiac pacemaking, repeated short contractions of the heart muscleare desired, followed by relatively long intervals of relaxation betweencontractions. In contrast, if sphincter rectalis stimulation is tocontrol anal incontinence effectively, continuous contraction over along period of time must be achieved. Obviously, even a single briefrelaxation of the sphincter over a period of many hours could result inincontinence when the patient relies entirely upon the electricalstimulation.

SUMMARY AND OBJECTS OF THE INVENTION Accordingly, the present inventionis directed to controlling anal incontinence and eliminating itsphysical inconvenience and psychological embarrassment. The aim is toaccomplish this by means of electrical stimulation of the sphincterrectalis, resulting in continuous tonic and physiological contraction ofthe sphincter muscle without lapses over long periods of time so as toachieve total continence.

At the same time, however, it is an object ofthe invention to accomplishthese results with minimal amounts of electrical power, both for medicalreasons and reasons of product design. The medical reasons involve theavoidance of injury to the adjacent tissue through electrical burns, aswell as avoiding over-stimulation of the tissue with consequent loss ofmuscle contraction response.

So far as product design is concerned, it would be quite desirable toprovide electrical stimulation apparatus for the control of analincontinence which will operate for long periods of time on the energyavailable from a small battery power supply. This would make theapparatus completely portable, allowing the patient to live as normal alife as possible. This is another consideration which dictates a designaiming at minimal power consumption.

The present method for the control of anal incontinence comprises thesteps of putting a pair of spaced electrodes against the sphincterrectalis and applying a signal across these electrodes which iseffective to maintain the sphincter in a continuously contractedcondition for the duration of the signal. In more specific terms, thesignal is a voltage varying at a rate in the range from about I8 toabout 90 Hertz, having an average potential of zero so as to avoidtissue polarization, and a substantially square waveform with a peakpotential of not more than about 2 volts.

The apparatus for practicing this invention comprises a probe includinga suppository body formed of a physiologically inert insulatingmaterial, and including a rounded bulbous tip adapted for insertion intoand subsequent retention within the anus of the patient. A reduced neckis joined at one end to the bulbous tip, and a broadened hilt at theother end of the neck serves to limit anal insertion of the device. Thereduced neck rests against the sphincter rectalis when the device isinserted, and has spaced-apart electrical contacts mounted thereon.These contacts are formed of a physiologically inert conductivematerial, and they serve to stimulate the sphincter electrically duringuse of the device. A pair of electrical leads is provided for therespective contacts, the leads coming out of the probe and beingconnected to the type of electrical drive described in the previousparagraph. Additionally, the broadened hilt of the suppository body hasa substantially flat base to permit the patient to sit or lie downcomfortably when the device is inserted.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view of arectal probe according to the present invention.

FIG. 2 is a front view partly in section and partly in elevation of thesame probe.

FIG. 3 is a schematic circuit diagram of the presently preferredelectrical generator for energizing the electrodes of the probe.

FIG. 4 is a diagram showing the response of normal dogs to threedifferent types of electrical stimulation of the sphincter rectalis.

FIG. 5 is a graph showing corresponding data in relation to dogssuffering from experimentally induced loss of sphincter rectalisfunction.

And FIG. 6 is a graph of sphincter rectalis response as a function ofthe electrical stimulation frequency.

The same reference characters refer to the same elements throughout theseveral views of the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The sphincter rectalisstimulation apparatus of this invention includes a rectal probe 8 of thetype illustrated in FIGS. 1 and 2. This probe comprises a suppositorybody 10 integrally molded of a physiologically inert material such assilicone rubber, medical grade, to avoid tissue necrosis. This materialis available from the Dow Chemical Company under the trademarkElastomer. The suppository body 10, which is inserted into the anus ofthe patient, is formed with a rounded bulbous tip 12 adapted for smoothinsertion with a minimum of discomfort to the patient. The bulbous tip12 tapers to a reduced neck 14, which then widens out again to abroadened hilt l6, terminating in a substantially flat base 18. Afteranal insertion has been accomplished, the fact that the bulbous tip 12has a larger diameter than the reduced neck 14 facilitates retention ofthe suppository body 10 by causing the body 10 to be cammed inwardlyinstead of being expelled in response to sphincter contraction. Thebroadened hilt 16, which is also wider than the reduced neck 14, servesto limit insertion of the suppository body 10 so that it is not intrudedtoo far into the anal opening.

As a result, the body 10 comes to rest with the reduced neck 14 claspedby the sphincter rectalis, the bulbous tip 12 protruding into therectum, and the broadened hilt 16 remaining outside the ans. When it isnecessary to remove the probe 8, the external portion 16 is thus readilyaccessible to facilitate withdrawal. As an additional feature of thesuppository body 10, the flat base 18 thereof permits the patient to sitor to lie down upon his back in relative comfort when the device is inuse.

The probe 8 also includes a pair of electrodes 20 and 22 mounted onopposite sides of the reduced neck 14 for electrical stimulation of thesphincter rectalis. Each of these electrodes is a thin leaf ofphysiologically inert but electrically conductive material, such asgold, although stainless steel and other relatively inert conductors maybe used. Preferably, the leaves 20 and 22 are formed of a plurality ofside-by-side wires 23 although satisfactory results can be obtained withthin continuous leaf material. The choice of silicone rubber as thematerial for the suppository body is of course entirely compatible withthe use of stainless steel for the contacts and 22, and in additionprovides electrical insulation between the contacts. While there are anumber of possible methods for securing the contacts 20 and 22 in placeupon the suppository body 10 the presently preferred method is to formthe contacts of thin leaves of gold which are bent to match thecurvature of the reduced neck 14 and are then simply glued in place. Anymethod will do, however, if it results in contacts 20 and 22 which lierelatively flat against the surface of the reduced neck 14 so as toavoid injury to the patient upon insertion.

in order to provide individual electrical connections to the contacts 20and 22, the suppository body 10 may be provided with a hole 24 drilledtransversely through the reduced neck 14, and another hole 26 drilledlongitudinally upward from the base 18 and intersecting the transversehole 24. A pair of leads 28 and 30 enter the longitudinal hole 26 fromoutside the base 18, and extend upwardly through the length of thelongitudinal hole to the transverse hole 24. Then the leads 28 and 30extend in opposite directions through the transverse hole 24 to reachtheir respective electrical contacts 20 and 22, to which they aresoldered. When mounting the electrical contacts 20 and 22 upon thesuppository body 10, the leads 28 and 30 can first be inserted into theholes 26 and 24, and pulled sidewardly from the ends of the hole 24 sothat a length of each lead protrudes from the reduced neck 14 tofacilitate soldering to the associated contact. Afterwards, the leads 28and 30 can be pulled back down through the longitudinal hole 26 whilethe contacts 20 and 22 are placed adjacent the reduced neck 14 and gluedin place.

In order to enable workers in the field to practice this inventionreadily, it will be helpful to have some idea of the dimension of therectal probe 8 which enable it to fit comfortably and functionallywithin the rectal opening of a patient. In a particular preferredembodiment, the overall length of the suppository body 10 from the base18 to the tip of the rounded bulbous tip 12, was about 3 inches. Themeasurement from the extremity of the rounded bulbous tip 12 to thethinnest portion of the reduced neck 14 was approximately 1% inches. Themaximum diameter of the tip 12 was approximately 1% inches, and theminimum diameter of the reduced neck 14 was approximately one-half inch.The maximum diameter of the broadened hilt 16 should be somewhat inexcess of the maximum diameter of the rounded bulbous tip 12. Thecontacts 20 and 22 were approximately one-quarter inch wide and 1%inches long. They were so placed upon the reduced neck 14 that theyextended to within about half an inch of the base 18.

Best experimental results were achieved with an electrical signal ofsquare wave shape applied across the contacts 20 and 22 by means of theleads 28 and 30. One illustrative circuit which has been found toaccomplish this successfully is illustrated in FIG. 3. There it is seenthat a battery 32 energizes a positive bus and a negative bus 42 throughan on-off switch 38.

A conventional unijunction relaxation oscillator 56 energized frombusses 38 and 42 serves to generate repetitive pulses for timing thesquare wave output signal. The time base is an RC circuit comprising acapacitor 58 charging through a series resistance 60. The switchingfunction for the relaxation oscillator is accomplished by a unijunctiontransistor 64, the emitter E (switching electrode) of which is connectedto the positive side of the timing capacitor 58. Load current for theunijunction is drawn through a resistor 66 in series with base B2 and aresistor 68 in series with base B1.

The relaxation oscillator operates in the following well known manner.lnitially, the unijunction 64 is cut off, and the timing capacitor 58charges through the resistance 60. When the capacitor voltage reachesthe threshold switching potential of the unijunction 64, the unijunctionturns on, and timing capacitor 58 then discharges through the emitterand base 1 of the unijunction and the resistor 68. When the dischargingprocess drops the unijunction emitter voltage below the cutoff level,the unijunction 64 ceases conducting and the charging cycle startsagain. Since the value of the resistor 60 determines the RC timingconstant, it determines the capacitor charging time, which in turndeterminesthe pulse repetition rate.

The output of the unijunction relaxation oscillator 56 is a train ofpositive pulses developed across the load resistor 68 by the successivedischarges of the timing capacitor 58 through the emitter-base 1 circuitof the unijunction 64. This pulse train has good frequency stability,which is one of the characteristic advantages of unijunction time basecircuits.

The unijunction output pulse train is applied over a lead 70 to abistable circuit or flip-flop 72. Each successive output pulse from therelaxation oscillator 56 reverses the state of the bistable circuit 72in the following manner. The bistable circuit comprises twoNPN-transistors 74 and 76, and two PNP- transistors 78 and 80. These aregrouped into two diagonal pairs 74, 80 and 76, 78, with each diagonalpair of transistors conducting simultaneously, and alternatingconduction with the other diagonal pair. Assume that at a given momenttransistor 80 is conducting. its collector load current flows through apair of resistors 82 and 84 which form a voltage divider. The potentialat the center point of the voltage divider 82, 84 drives the base oftransistor 74 high to make the latter transistor conduct at the sametime that transistor 80 is conducting.

When the next output pulse from relaxation oscillator 56 appears on thelead 70, it is applied through an isolating diode 86 to the base oftransistor 74, but has no effect on that transistor because it isalready conducting. The same output pulse however is also appliedthrough another isolating diode 88 to the base of transistor 76, turningthat transistor on. When this happens, the collector potential oftransistor 80 drops due to the low impedance path presented by the nowconducting transistor 76, and as a result the positive base driveformerly transmitted to transistor 74 through resistor 82, is nowterminated, and as a result transistor 74 turns off. When transistor 74turns off, it ceases to draw collector current through the voltagedivider formed by resistors 90 and 92. This removes the negative basedrive from transistor 80, which consequently also shuts off. At the sametime, the collector current now drawn by transistor 76 traverses thevoltage di vider formed by the resistors 94 and 96. The resultingnegative base drive to the transistor 78 turns that transistor on. Itwill therefore be appreciated that the effect of the oscillator outputpulse appearing on lead 70 and coming through the diode 88, is to turntransistors 76 and 78 on, while cutting transistors 74 and 80 off. Ineffect, the flip-flop 72 is switched.

Thereafter, the flip-flop remains in the state to which it has beenswitched, because the collector current of transistor 78 flows throughthe voltage divider comprising resistors 98 and 100, and the resultingvoltage developed across resistor 100 provides the necessary positivebase drive to transistor 76 to keep the latter in conduction. At thesame time, the collector current of transistor 76 flows through thevoltage divider comprising resistors 94 and 96, so that the voltagedeveloped across resistor 94 provides the necessary negative base driveto keep transistor 78 in conduction.

The next positive output pulse from the oscillator 56 appearing on lead70 will switch the flip-flop 72 back again. This pulse passes throughthe diode 88 but has no effect on transistor 76 because the latter isalready conducting. However the pulse, in passing through diode 86 aswell, turns on transistor 74. This in turn causes transistor 80 to turnon and transistors 76 and 78 to turn off. This state also is stable,continuing until the next oscillator pulse occurs. The process need notbe described in detail because it is precisely the complement of theswitching operation described above.

Since the bistable circuit 72 stays in each of its two conducting statesuntil the occurrence of the next output pulse from the relaxationoscillator 56, the circuit 72 will spend equal time (on the average) ineach of its two stable states, provided the consecutive output pulsesfrom the oscillator 56 are evenly spaced (on the average). Sinceunijunction relaxation oscillators are noted for their frequencystability, this condition is met. As a result, over any substantialnumber of full cycles of operation, each state of the bistable circuit72 will average out to substantially a 50 percent duty cycle. This isimportant, because it permits the average potential of the electricalstimulation applied to the sphincter rectalis to be zero. This avoidselectrical polarization of the biological tissue, which would have quiteundesirable effects as described subsequently. It should also be notedthat the value of the resistor 60 determines the pulse repetition rateof the relaxation oscillator 56 so as to select the desired operatingfrequency, but does not affect the 50 percent duty cycle. The outputpulses from the relaxation oscillator 56 can be closer together orfurther apart in time as determined by the value of the resistor 60, butas long as they occur at a steady rate for any given resistance value,the interval between successive reversals of the bistable circuit 72will be equal.

When the transistors 78 and 76 are conducting, output lead 30 isconnected through a resistor 102 to the high collector potential oftransistor 78, while output lead 28 is connected through a potentiometer104 and resistor 106 to the substantially lower potential developedacross resistors 94 and 96 by the collector current of transistor 76.Accordingly, in this state of the bistable circuit 72, the output lead30 is driven high and the output lead 28 is driven low. After thebistable circuit 72 is switched to its opposite state, transistors 74and 80 are conducting and transistors 76 and 78 are cut off. At thattime the polarities of the output leads 28 and 30 are reversed becauselead 28 assumes the high collector potential of transistor 80, whileoutput lead 30 assumes the low potential developed across resistors 90and 92 as a result of the collector current of transistor 74. It willtherefore be understood that the output on the leads 28 and 30 is asquare wave synchronous with the switching frequency of the bistablecircuit 72. The output leads 28 and 30 of FIG. 3 are the same as theinput leads 28 and 30 to the contacts and 22 of FIGS. 1 and 2.Accordingly, the square wave output of the circuit of FIG. 3 is theelectrical drive used for stimulating the sphincter rectalis of thepatient.

The potentiometer 104, which is wired as a rheostat, serves to adjustthe load current drawn by the body tissues of the patient. The circuitis designed to have an output impedance such that even under shortcircuit conditions, the load current is of the order of a couple ofmilliamperes; therefore it is obvious that the current actually drawnthrough the impedance represented by the body tissues of the patientwill be substantially less, and therefore at a safe level. The resistors106 and 102 are in series with the output, and contribute to thelimiting of the output current. The capacitors 108 and 110 are includedin the circuit to bypass base transients of the transistors 78 and 80respectively.

While the circuits for the electrical generator of FIG. 3 are a matterof design choice, and the choice of parameters for and types of circuitelements in the illustrated electrical generator of FIG. 3 are withinthe ability of the skilled art worker, a highly desirable electricalgenerator in accordance with FIG. 3 has been employed in working thepresent invention using the following circuit parameters and elementdesignations.

Circuit Element Parameters or Designation Battery 32 5.6 v. Capacitor 5847 Microfarad 35 v. Resistor 60 68 Kohms k w. Unijunction Transistor 642N48S3 Resistor 66 680 ohms h w.

Resistor 68 82 ohms A w.

Transistor 74 MPF 6552 Transistor 76 MPF 6552 Transistor 78 2N 5087Transistor 80 2N 5087 Resistor 82 47 Kohms A w.

Resistor 84 47 Kohms I: w.

Diode 86 IN 9l4 Diode 88 IN 914 Resistor 90 47 Kohms A w.

Resistor 92 47 Kohms 56 \v.

Resistor 94 47 kohms Resistor 96 47 Kohms b w.

Resistor 98 47 Kohms 5: w.

Resistor 100 47 Kohms A w.

Resistor I02 270 ohms V: w.

Potentiometer I04 Max R=5 Kohms Resistor 106 270 ohms V: w.

Capacitor 108 .02 microfarad 50 v. Capacitor I10 .02 microfarad 50 v.

It will be understood that the above defined circuit elements areincorporated herein by way of illustration and not by way of limitation.

The therapeutic effect of the apparatus of FIGS. 1 through 3 is bestdescribed in terms of the experimental results actually obtained.Comparative studies have been performed on normal and paraplegic dogs,the normal group serving as a scientific control while the paraplegicdogs gave an indication of the ability of this invention to restore lostfunction of the sphincter rectalis. In the test group, paraplegia of thesphincter was experimentally induced by either of two methods, spinalanesthesia with xylocaine, or transsection of the spinal cord in thelumbar area. In both cases, fecal incontinence appeared quite promptlyas a result, and this was thought to be analogous to naturally occurringneurogenic sphincter rectalis dysfunction.

An electrical stimulation device similar to that of FIGS. 1 aNd 2, butproportioned to the experimental animals, was inserted into the rectalopening so that the sphincter rectalis clasped the reduced neck 14thereof, thereby coming in contact with the spaced electrodes 20 and 22.In other cases, the output electrodes used for the purpose of electricalstimulation were in the form of needles inserted directly into thesphincter muscle on opposite sides of the anus of the experimentalanimal. In the terminology used for the purposes of this patentapplication and the appended claims, any reference to an electrodeplaced against the sphincter rectalis, or similar terminology, should beunderstood to apply generically to both types of electrode placement,i.e., placement of the electrode in contact with the epidermis overlyingthe sphincter rectalis, as well as insertion of the electrodes throughthe epidermis and directly into the sphincter muscle itself.

Pressure changes within the anal canal of the experimental animals, justinside the sphincter rectalis, were monitored by insertion of a smallrubber balloon filled with water and connected to a water manometer. Inthe first series of tests, the stimulation frequency was 20 Hertzthroughout, and water pressure changes were plotted as a function ofpeak voltage for three different types of wave forms: low duty cyclepulses, sine wave, and square wave. FIG. 4 graphically illustrates theresults obtained with normal dogs. Trace 112 shows that, for square waveenergization, the water pressure obtained increased from a low value atan energization level of 1 volt peak, to over 115 millimeters of waterat an energization potential of somewhat more than 5 volts peak. Trace114 shows the corresponding results for sine wave stimulation as thepeak voltage was varied. Trace 116 is the corresponding curve for a lowduty cycle pulse wave form. The conclusion drawn from the graph of FIG.4 is that with normal dogs, the square wave (trace 112) gives maximumresults with minimum power consumption and lowest peak voltage levels.

The results were somewhat different for the paraplegic dogs, as shown inthe graph of FIG. 5. The onset of reaction to stimulation with all threekinds of signals, the square wave signal represented by trace 118, thesine wave signal represented by trace 120, and the low duty cycle pulsewave form represented by trace 122, occurred at a lower voltage level,and hence a lower power level. In addition, above 2 volts the trace 120corresponding to the sine wave rises steeply and after a certain pointexceeds the response represented by the square wave trace 118. Thishowever does not necessarily lead to the conclusion that sine wavestimulation is superior.

In the treatment of fecal incontinence by means of electrostimulation ofthe sphincter rectalis muscle, the goal is to restore normal muscularcontraction in order to close the anal opening in a physiologicalmanner. In the course of the experiments performed on dogs, it wasobserved that the difference in anal canal pressure before and after theexperimental induction of paraplegia, was only between 12 and 15millimeters of water. (This value might be slightly greater in cases ofchronic paraplegia, as a result of progressive atrophy of the sphinctermuscle.) Since this is not a very great pressure difference, it is notnecessary to produce a muscular contraction which would increase theanal pressure to the extreme values achieved by the sine wave trace 120when the peak potential rises much above 2 volts. Moreover, suchpressures would be unphysiological. For effective anal pressures notexceeding 35 millimeters of water, square wave stimulation (representedby trace 118) allows for the lowest electrical power and voltage levelsfor a given pressure response. Since it is desirable to keep theelectrical energy level as low as possible in order to avoid tissuedamage or overstimulation and consequent fatigue of the muscle, itfollows that a square wave output is the method of choice.

In fact the application of excessive electrical voltage and power levelsresulted in clonic contractions, not only of the sphincter rectalismuscle, but over the entire perineal area, and extending into theextremities. The onset of such spasms is marked with xs and indicated byarrows 124 on the graph traces 112, 114, 118 and 122 (FIGS. 4 and 5).Such contractions are of course undesirable in themselves, and inaddition the graphs of FIGS. 4 and 5 show that after the onset of cloniccontractions the degree of response to the applied stimulus had atendency to fall off.

FIG. 6 demonstrates the variation of pressure response as a function ofchanges in frequency. As the graph of FIG. 6 shows, the response felloff rapidly below 18 Hertz, while at frequencies above 90 Hertz theresponse was short muscular twitches followed by intervals ofrelaxation, rather than the desired tonic contraction. At frequenciesbetween 18 and 90 Hertz. the response was substantially uniform, and theresults not greatly affected by the specific choice of frequency withinthat range.

Accordingly, it appears that the method of choice for the presentpurpose is electrical stimulation of the sphincter rectalis by means ofa square wave having a peak potential not greater than about 10 voltsand preferably between about 1 and 2 volts, and a frequency in the rangefrom 18 to 90 Hertz.

It is important to note that one of the advantages of square wavestimulation is the fact that such a wave form has an average potentialof zero. This avoids polarization of the muscle tissue to which theelectrical stimulation is applied. If a direct current is conductedthrough muscle tissue and continued for upwards of about 4 minutes, themuscle becomes polarized and relaxes. Then a new contraction cannot beproduced by the same method for an interval of about 10 minutes. Thecontrol of incontinence, however, requires constant muscular contractionover long periods of time. A gap of 10 minutes in the protectionafforded by electrical stimulation can easily result in fecalincontinence, thereby defeating the purpose.

Moreover, it has been noted that a device constructed and used in themanner described controls urinary incontinence as well as analincontinence. Thus with paraplegic patients who generally exhibit bothanal and urinary incontinence, the use of the one device will controlboth conditions. Accordingly, when a patient using the devicedeenergizes it for the purposes of eliminating feces, he can expectsimultaneous urination.

It will now be realized that the method and apparatus of the presentinvention provide significant advantages in the control of rectalincontinence and the obvious physical inconvenience and psychologicalembarrassment which such a condition entails.

Since the foregoing description and drawings are merely illustrative,the scope of protection of the invention has been more broadly stated inthe following claims, and these should be liberally interpreted so as toobtain the benefit of all equivalents to which the invention is fairlyentitled.

The invention claimed is:

1. The method of controlling anal incontinence due to failure of thesphincter rectalis function, comprising the steps of:

putting a pair of spaced electrodes against the sphincter rectalis;

applying an alternating signal having an average value of about zeroacross said spaced electrodes to contract said sphincter rectalis, and

maintaining said sphincter in a steady contracted condition bycontinuing to apply said signal to said electrodes.

2. The method of claim 1 wherein said signal is a voltage having afrequency rate in the range from about 18 to about Hertz.

3. The method of claim 2 wherein said signal is substantially a squarewave.

4. The method of claim 3 wherein the peak potential of said signal isnot greater than about 10 volts.

5. The method of claim 3 wherein the peak potential of said signal isbetween about 1 and 2 volts.

6. ln apparatus for use in controlling incontinence, a rectal probeincluding:

a suppository body formed of an insulating material and including arounded bulbous tip adapted for insertion into and subsequent retentionwithin the anus of a patient, a reduced neck joined at one end to saidbulbous tip, and a broadened hilt joined to said reduced neck at theother end thereof to limit anal insertion of said suppository device sothat said reduced neck rests against the sphincter rectalis;

and a pair of spaced-apart electrical contacts energizable by anexternal voltage source and secured to the external surface of saidreduced neck whereby to rest against said sphincter rectalis duringinsertion;

a pair of electrical leads for connection to said external voltagesource and connected to said contacts respectively for energizationthereof; and

an electrical generator connected to said leads for energizing saidcontacts, said generator comprising:

a time base oscillator for producing a series of timing pulses;

and a bistable circuit arranged to switch between alternate states inresponse to successive ones of said timing pulses, and to apply asubstantially square wave output to said leads as a result of saidswitching.

1. The method of controlling anal incontinence due to failure of thesphincter rectalis function, comprising the steps of: putting a pair ofspaced electrodes against the sphincter rectalis; applying analternating signal having an average value of about zero across saidspaced electrodes to contract said sphincter rectalis, and maintainingsaid sphincter in a steady contracted condition by continuing to applysaid signal to said electrodes.
 2. The method of claim 1 wherein saidsignal is a voltage having a frequency rate in the range from about 18to about 90 Hertz.
 3. The method of claim 2 wherein said signal issubstantially a square wave.
 4. The method of claim 3 wherein the peakpotential of said signal is not greater than about 10 volts.
 5. Themethod of claim 3 wherein the peak potential of said signal is betweenabout 1 and 2 volts.
 6. In apparatus for use in controllingincontinence, a rectal probe including: a suppository body formed of aninsulating material and including a rounded bulbous tip adapted forinsertion into and subsequent retention within the anus of a patient, areduced neck joined at one end to said bulbous tip, and a broadened hiltjoined to said reduced neck at the other end thereof to limit analinsertion of said suppository device so that said reduced neck restsagainst the sphincter rectalis; and a pair of spaced-apart electricalcontacts energizable by an external voltage source and secured to theexternal surface of said reduced neck whereby to rest against saidsphincter rectalis during insertion; a pair of electrical leads forconnection to said external voltage source and connected to saidcontacts respectively for energization thereof; and an electricalgenerator connected to said leads for energizing said contacts, saidgenerator comprising: a time base oscillator for producing a series oftiming pulses; and a bistable circuit arranged to switch betweenalternate states in response to successive ones of said timing pulses,and to apply a substantially square wave output to said leads as aresult of said switching.